Wireless communication networks typically divide a radio network into cells, and a mobile station in a particular cell is provided with service from a base station in that cell. When the mobile station travels from one cell to another cell, a handoff of the mobile station from the first base station to a second base station is performed to ensure continuous service for the mobile station. A handoff transfers control of the mobile station to the second base station.
Handoffs are generally divided into soft handoffs and hard handoffs. For a soft handoff, service is concurrently provided by the first base station and the second base station, after which service by the first base station is disconnected. For a hard handoff, service provided by the first base station is disconnected before service begins to be provided by the second base station. Thus, soft handoffs may be preferred to ensure that calls are not inadvertently dropped. However, some systems, such as Orthogonal Frequency-Division Multiple Access (OFDMA) systems, fail to provide a mechanism for accomplishing soft handoffs.
Therefore, there is a need in the art for improved OFDMA networks that allow a soft handoff of a mobile station from one base station to another. In particular, there is a need for an OFDMA network that is able to provide communication on a downlink from each of two base stations to one mobile station and/or on an uplink from one mobile station to each of the two base stations in order to allow the performance of a soft handoff of the mobile station.